For far too long I’ve been hearing about random bounces on my email addresses (all of which are routed by postfix to my gmail account). The bounce messages contain something like :
The reason for this weirdness (according to this) is
postfix is configured for IPV4 and IPV6, then it will attempt to contact the next server using a ‘protocol at random’.
However, gmail accepts a mail from an IPV6 connection BEFORE verifying that the PTR records, etc match up. Google then proceeds to
bounce the email - even though if it had been contacted over IPV4 the mail would have been accepted.
Rather than fiddle around with IPV6 PTR records (which relies on every element on the chain behaving flawlessly, some of which are not controlled by me),
the simplest thing to do is to change my (targetted) relay
postfix server to claim to be only IPV4-enabled.
Update via Webmin
I could not find the setting that adjusts
inet_protocols in the interface directly, so had to
edit the configuration file
/etc/postfix/main.cf via the
Edit Config Files icon on the Postfix main Webmin page.
Inside the file, find the line :
and change it to :
Even though Webmin has updated the config file, the server doesn’t restart automatically to accept the new setting.
To see this in action, first have a look at the protocols that
postfix is claiming (where
:: is standing for IPV6 addresses):
Afterwards, only the IPV4 addresses are claimed :
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